1. Field of the Invention
The present invention generally relates to a wireless mobile communication system, and in particular, to a system and method in which a Mobile Station (MS) selects a serving node in a multi-hop wireless mobile communication system using a multi-hop method.
2. Description of the Related Art
Generally, the operation in which an MS selects a Base Transceiver Station (BTS) to which a communication link for transmitting and receiving a signal is to be connected in a multi-hop wireless mobile communication system is referred to as a serving node selection operation. The serving node selection operation occurs during a cell selection operation and a handover operation. In the cell selection operation, the MS selects a cell (i.e., a BTS) to which the communication link is to be connected when the MS is powered on or when a previously disconnected MS re-enters a service coverage area. In the handover operation, the MS moves from its current serving BTS to a new BTS, i.e., a target BTS.
When the MS performs the cell selection operation and the handover operation in a general wireless mobile communication system, the MS uses the reception quality, e.g., an energy-to-noise ratio (Ec/I0) value, of a reference signal, e.g., a pilot signal received by the MS in a cell. The MS measures average Ec/I0 values of pilot signals received from a plurality of BTSs and selects a BTS that transmits a pilot signal corresponding to the maximum average Ec/I0 value as its serving node.
In the field of a 4th-Generation (4G) communication system as a next generation communication system, extensive research has been actively is being conducted to provide multiple services having high transmission speeds and various Quality of Service (QoS). One of the techniques for meeting the performance requirements of the 4G communication system is a multi-hop method.
The multi-hop method not only increases a data transmission rate with low cost but also extends a service coverage area using a relay node. In a general wireless mobile communication system, all MSs are directly connected with a BTS to be provided with a service from the BTS. However, in the multi-hop wireless mobile communication system, a relay node for relaying a signal is additionally included and thus the MS is provided with a service from the BTS or a multi-hop relay node connected with the BTS through a multi-hop node.
When the MS is provided with a service by being connected to the multi-hop relay node, the MS receives a signal transmitted from the BTS through the multi-hop relay node. A delay may occur in the services provided to the MS due to overhead resulting from the relay operation. For example, if the MS receives a signal transmitted from the BTS through two hop nodes, i.e., a first multi-hop relay node and a second multi-hop relay node, in the multi-hop wireless mobile communication system, a service delay occurs due to signal relay operations between the BTS, the first multi-hop relay node, and the second multi-hop relay node when compared to when the MS receives a signal directly from the BTS.
Since the serving node selection operation in the multi-hop wireless mobile communication system has an important influence upon QoS, it is a core part of the multi-hop wireless mobile communication system. There emerges a need for a serving node selection method for a multi-hop wireless mobile communication system, which minimizes a service delay and relay overhead.